1. Field of the Invention
The present invention relates to heat exchanger connections and, in particular, to a method and system for aligning and connecting transmission oil cooler lines to a motor vehicle radiator containing a transmission oil cooler.
2. Description of Related Art
Replacement radiators for trucks almost always contain a transmission oil cooler installed in one of the coolant tanks of the radiator assembly. When replacing the radiator, the transmission oil lines must first be disconnected from the oil cooler and then reconnected after the replacement radiator is in place. The oil lines use small diameter steel tubing and the fitting on each oil line used to connect it to the oil cooler is also typically steel. The vast majority of oil coolers are brass and since the oil inlet and outlet fittings are brazed to the oil cooler, they too are brass. The remainder of the oil coolers are steel, with steel fittings.
FIG. 1 shows prior art oil cooler 22 mounted within the wall 20 of an otherwise conventional radiator tank. A flange 23, at one end of the cylindrical cooler inlet extension 28, is sealed to the tank wall 20 by gasket 24. Inlet extension tube 28 extending from the flange passes through an opening in the radiator tank wall 20 and has on the free end internal 32 and external 30 threads. The oil cooler 22 is secured to the tank wall 20 by nut 40 which has internal threads which mate with tube extension external threads 30, to hold the oil cooler securely. Nut 40 is typically a Palnut brand threaded fastener (available from Tinnerman Palnut Engineered Products of Brunswick, Ohio), made of formed sheet steel which has hex shaped external sides 42. The oil cooler tube extension 28 further has an inner flared opening 26 which receives and seals to an oil supply line.
As also shown in FIG. 1, oil supply line 60 has a flared end 64 to mate with the flare of oil cooler opening 26. The tubing nut 50 has exterior hex sides 54 and a threaded portion 52 to engage threads 32 inside the oil cooler extension tube 28.
Problems occur when attempting to reconnect the transmission oil lines to the oil cooler with the replacement radiator in place in the vehicle. Because of typically poor accessibility and visibility, in many instances the installer inadvertently does not properly align the fittings on the transmission lines with the corresponding fittings on the oil cooler. Such problems are made worse in the vast majority of the time when one of the fittings is brass (e.g., the one brazed to the oil cooler) and the mating fitting is steel. Since brass is softer than steel, the probability of cross threading on the oil cooler fitting greatly increases. The damage is difficult to repair since it involves the radiator. Even if the oil cooler fitting is steel, cross threading can still occur. If the damaged fitting is an integral part of a large component, as the radiator assembly usually is, then the entire radiator may have to be replaced, or at least removed from the vehicle and the oil cooler professionally replaced, which is both expensive and time consuming.
Consequently, there is a need for a method and system to establish and maintain near perfect alignment between such fittings as the tube fitting is threaded into the oil cooler fitting, to eliminate the high incidence of misaligned threads and the resulting high warranty costs. There is also a need for a means to limit the sealing torque, to prevent thread stripping while still providing the required sealing torque.